main as it stood before the decl2 line was merged. Bookmark taken before merging decl2, which adds PhasedObserveImmutable, its docs, and the additions made for the wield.model migration. Deliberately free of digits: setuptools_scm / vcs_versioning selects tags with 'git describe --match *[0-9]*', so a marker named 'pre-decl2' was picked up as if it were a version and failed to parse.